Looks very much to me like sidearms worn by specialist troops in European armies. These heavy bladed weapons were worn by the units that corresponded to engineers in U.S. troops, but were known by terms such as sappers (for the French term for an excavated trench) or in Germany as pioneers. There were many variations of these 'technical' forces, and these sidearms were for utility or weapons as required. Many of these, as in Austria or Germany had sawtooth backs (see Wagner "Cut and Thrust Weapons").
It seems many bayonets had these features as well.

I cannot tell by the size of the photo here, and if this seems larger than a normal bayonet, as in the size of a large hanger, this is likely what it is.
It appears to be 20th c. possibly WWI period. It seems most of the 19th century forms of these had brass hilts.